It may be useful, in a variety of settings, to utilize both a traditional engine (e.g., an internal combustion engine) and one or more infinitely variable power sources (e.g., an electric motor/generator or hydraulic motor/pump, a variable chain drive, and so on) to provide useful power. For example, a portion of engine power may be diverted to drive a first continuously variable power source (“CVP”) (e.g., a first electric motor/generator acting as a generator, a first hydrostatic or hydrodynamic motor/pump acting as a pump, and so on), which may in turn drive a second CVP (e.g., a second electric motor/generator acting as a motor using electrical power from the first electric motor/generator, a second hydrostatic or hydrodynamic motor/pump acting as a motor using the hydraulic power from the first hydrostatic or hydrodynamic motor/pump, and so on).
In certain applications, power from both types of power sources (i.e., an engine and a CVP) may be combined for delivery of useful power (e.g., to drive a vehicle axle) via an infinitely variable transmission (“IVT”) or continuously variable transmission (“CVT”). This may be referred to as “split-mode” or “split-path mode” because power transmission to a vehicle (or other) power sink may be split between a mechanical path from the engine and an infinitely/continuously variable path through one or more CVPs. In other applications, in contrast, useful power may be provided to power sinks from the engine (e.g., via various mechanical transmission elements, such as shafts and gears), but not from a CVP. This may be referred to as “mechanical-path mode.” It will be understood that various non-mechanical power transmission devices, such as torque converters, may sometimes be used in the mechanical-path mode. In this light, a mechanical-path mode may be viewed simply as a power transmission mode in which the engine, but not the CVPs, provides useful power to a particular power sink.